This invention relates to an image forming method and an image forming apparatus.
In recent years, in an image forming apparatus based on an electrophotographic method, it is required to make toner particles have small particle diameter; as regards a method for obtaining such toner particles, for example, a polymerization method such as a suspension polymerization method or an emulsion polymerization method has been appropriately utilized.
However, as the result, with the toner particles being made to have small particle diameter, the adhering force of toner particles to an image carrying member becomes larger, it is produced a problem that, by a cleaning device, for example, of a cleaning blade method in which residual toner particles on an image carrying member are removed by rubbing the surface of the image carrying member with a cleaning blade in pressing contact with it, it becomes extremely difficult to remove residual toner particles such as un-transferred toner particles or after-transfer residual toner particles on the image carrying member. In particular, in the case where what is called a polymerization toner produced by a polymerization method is used, in addition to the factor of the particle diameter, because the shape of the toner particles becomes near to a sphere, occurrence of poor cleaning, that is, what is called “passing through” phenomenon in which toner particles roll on the image carrying member to pass under the cleaning blade, occurs remarkably.
In order to prevent the above-mentioned occurrence of poor cleaning, a cleaning method in which mechanical cleaning with a cleaning blade and electrostatic cleaning are both used is disclosed in the publication of the unexamined patent application H3-179675 etc.
To state it concretely, it has a structure such that, at an upstream position of a cleaning blade with respect to the moving direction of the image carrying member, a brush roller made of an electrically conductive material is mounted, and a suitable-magnitude bias voltage having the reverse polarity to the residual toner particles on the image carrying member is applied to this brush roller, and it is intended to improve the cleaning performance by the mechanical cleaning effect of the cleaning blade and the electrostatic cleaning effect of the brush roller.
However, it has been proved that, even in an image forming apparatus equipped with a cleaning device of a cleaning method as described in the above, it was difficult to remove residual toner particles on an image carrying member with certainty, and image defects such as background density and white streaks or black streaks due to the contamination of the charging electrode in the charging means were produced, which made it difficult to form a high-quality image after all.